Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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757
FXUS63 KGRR 201200
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
700 AM EST Mon Nov 20 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EST Mon Nov 20 2017

A relatively quiet period is expected into mid week as no major
weather system are forecast to affect the area. We may see a bit of
light rain on Tuesday along and ahead of a cold frontal passage. In
its wake Tuesday afternoon into Wednesday morning a bit of lake
effect snow will occur. Little to no snow accumulation is expected
however. We will see highs both today and on Tuesday in the 40s.
Temperatures will tumble again behind the Tuesday cold front with
high on Wednesday only forecast to reach the 30s. The Thanksgiving
outlooks is for good travel weather across Southwest Lower Michigan
with dry weather and high temperatures around 40.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EST Mon Nov 20 2017

Limited concerns in the short term period. A southwesterly gradient
builds in quickly today with breezy conditions expected. Dry weather
is forecast today and tonight as we will be in the warm sector of a
clipper system passing well off to our north. Highs today will push
into the 40s, more typical for this time of year as compared to the
colder 30s we had on Sunday.

Tuesday the cold front will push southeast through the forecast
area. We will likely see some scattered rain showers develop along
and ahead of the front. The best chances to see showers will be in
the southeast towards Jackson.

The cold air advection is strong in the wake of the front with delta
T`s climbing to around 20C during the late afternoon. Moisture is
not great but we will likely see some light lake effect snow showers
developing. The snow showers will continue Tuesday night into
Wednesday morning with little to no accumulation.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EST Mon Nov 20 2017

Precipitation will be mostly toward the end of the long term as high
pressure will be moving across the state during the middle of the
week. Both the gfs and ecmwf are in pretty good agreement with the
track and strength of low pressure as it crosses southern Ontario
Friday. The trailing cold front will get some support aloft via a
short wave as it moves across northern Lower. Highest pops will be
Friday evening just ahead of the cold front and across the northern
cwa. This is basically a rain event, although a few wet snowflakes
may mix in over the far northeastern cwa late Friday night and
Saturday morning. Behind the front, another shot of cold air will
flow south. However, the system looks similar to the one that just
moved through a couple of days ago. H8 temps fall to around -12c and
moisture is shallow. We include low chc pops for snow
showers...mostly over the western cwa, but we don`t expect much out
of this system Saturday afternoon and night.

Highs will be in the 40s Thursday through Saturday before dropping
into the 30s Sunday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 700 AM EST Mon Nov 20 2017

The main weather feature the next 24 hours or through 12Z Tuesday,
will be the wind. A strong pressure gradient will build into the
area today with an increase in wind slated for late morning.
Southwest winds (200-220 degrees) at 15 to 30 knots are expected
at the TAF sites after about 15z to 16z. The strongest winds will
be at KMKG where winds will gust in excess of 30 knots this
evening and tonight. Winds tonight aloft, at 1000-2000ft will
reach speeds of 40-55 knots. It will remain breezy through tonight
at all sites.

Otherwise, VFR conditions are expected through tomorrow morning
with cloud bases at or above 15,000ft.

&&

.MARINE...
Issued at 330 AM EST Mon Nov 20 2017

With Gale conditions forecast within the first period have opted to
drop the Small Craft Advisory and upgrade to a Gale Warning. Gale
gusts may show up in the southern nearshore zones as early as late
morning or midday. The core of the Gale conditions will occur
tonight with 35 to 45 knot gales from the southwest. Waves will peak
in the 9 to 13 foot range. Winds and waves will gradually settle
down from Tuesday into Wednesday. The Gale Warning runs through mid
morning on Tuesday, when we will likely need a Small Craft Advisory
through midday on Wednesday.


&&

.HYDROLOGY...
Issued at 1145 AM EST Sun Nov 19 2017

Numerous streams and rivers across the southern half of Lower
Michigan will continue to show the affects of Friday`s and
Saturday`s rainfall. Rises are expected through the weekend before
rivers stabilize next week.

A quieter pattern is forecast through the Thanksgiving Day
period. Given current forecasts and river trends, all sites should
remain below flood criteria. Impacts are expected to remain minor
and immediately along streams and rivers.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Gale Warning until 10 AM EST Tuesday for LMZ844>849.

&&

$$

SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...04
AVIATION...Duke
HYDROLOGY...JAM
MARINE...Duke



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